1. Field of the Invention
The present invention generally relates to magnetic recording media heads and, more particularly, to a magneto-resistive (MR) head having modules with opposing MR read elements and opposing periodic structures.
2. Background Art
Magnetic recording heads write and read data to and from magnetic recording media such as tape. The improvement in data densities on media is due in large part to improvements made in the sensor or transducer used for reading and writing data. An improvement in read sensor technology has been realized with the magneto-resistive (MR) sensor. The MR sensor detects magnetic field signals as resistance changes in a MR stripe or element.
MR heads employ multiple MR elements for reading data from respective tape tracks. MR heads may include two read modules for reading data from a tape in forward and backward tape directions. Each read module includes at least one MR read element. Each MR read element has an active central MR region abutted on each end by permanent magnet stabilization regions (i.e., permanent magnets). One read module (i.e., the read forward module) includes a MR read element for reading a tape track in the forward direction of the tape. Another read module (i.e., the read backward module) includes a MR read element for reading a tape track in the backward direction of the tape. Of course, each read module may include additional MR read elements for reading additional tape tracks such that the MR tape head becomes a multi-track MR tape head. The MR read elements are identified as either data or servo MR read elements depending on whether they read data or servo tape tracks.
In order for a MR head to function properly, each MR read element needs to be biased and magnetically stabilized in order to achieve high linearity and low Barkhausen noise levels. In the construction of MR heads using a periodic structure (i.e., grating) for magnetically stabilizing the MR read elements, two separate wafers are manufactured for the build of the two individual read module dies. That is, a first wafer for the read forward module and a second wafer for the read backward module are manufactured. The first and second wafers each have their own unique grating or periodic structure orientation (for example, 45°) complementing the MR read element abutted permanent magnet stabilization regions, the deposited easy axis orientation for the MR read element, and the bias current direction in each of the two read modules.
That is, the grating or periodic structure orientations of the two wafers are directed along respective opposite first and second directions. Thus, the grating or periodic orientation of the first wafer for the read forward module is directed along the first direction. The grating or periodic orientation of the second wafer for the read backward module is directed along the opposite second direction.
During assembly of a MR head, one of the read forward and backward modules is flipped over with respect to the other one of the read modules in order to be assembled into the MR head. For instance, the read backward module is flipped over with respect to the read forward module. Consequently, the grating or periodic structure orientations of the first and second wafers are now directed along the first direction when the read backward module is flipped over. Thus, the gratings of the wafers are mirror images in an assembled MR head.
At the completed head level with the read backward module flipped over, the direction of the PM magnetization is set along the first direction of the grating or periodic structure orientation of the two wafers. The bias current direction is set in each of the two modules along the first or second direction to magnetically stabilize the MR read elements.
As described above, prior to the read backward module being flipped over, the direction of the grating or periodic structure orientation of the first and second wafers of the read forward and backward modules is directed along opposite directions. Consequently, prior to the read backward module being flipped over, the PM magnetization and the bias current of the read forward module are directed along the first direction or second direction, i.e., along or anti-parallel to the grating or periodic structure orientation of the first wafer, while the PM magnetization and the bias current of the read backward module are directed opposite to their respective directions in the read forward module, i.e., along or anti-parallel to the grating or periodic structure orientation of the second wafer.
In effect, the first and second wafers each have their own unique grating or periodic structure orientation. As a result, two different wafer designs are required for use with this manufacturing technique.
This manufacturing technique allows the magnetic orientation of the MR read elements (data and servo) to be completed at the head level after all process destabilization effects have occurred. However, as described above, this manufacturing technique requires added cost for building two discrete wafers, the need for two wafer designs, and the related manufacturing line balance concerns.
What is needed is a MR head which is assembled by using a single wafer design for the read forward and backward modules. That is, what is needed is a common grating or periodic structure orientation wafer design for the two wafers used in fabricating the read forward and backward modules of a MR head. Such a common or single grating wafer design would eliminate the added costs associated with using two different wafer designs, and reduce production control costs. Such a common grating wafer design would result in the read modules having a common grating or periodic structure orientation prior to assembly into a MR head. Subsequently, when one of the read modules is flipped over for assembly into a MR head, the read modules of the MR head would have opposite grating or periodic structure orientations.